出席國際學術會議報告 - 開放測試場正規化場衰理論值探討及量測不確定度之研究(III)A Theoretical Investigation of Normalized Site Atten

2005 年 10 月 20 日報告人姓名

林根煌服務機構

及職稱

中山大學電機系教授

時間會議地點

2005 年 07 月 03 日至 08 日 Washington, DC

本會核定補助文號

<研究計畫中核定>

NSC93-2213-E-110-008

會議名稱

(中文) 2005 年 IEEE 天線傳播國際研討會及 URSI 無線電科學會議

(英文) 2005 IEEE AP-S International Symposium & USNC/URSI National Radio Science Meeting

發表論文題目

(中文) 一種用來降低有限大小接地面之修正標準場地法

(英文) A modified standard site method to reduce the effect of a finite-size ground plane

一、參加會議經過

本次會議是由IEEE/AP-S 與 URSI 合辦的國際性研討會，在美國首都華盛頓(Washington, DC)舉行。會議有 6 天，其中有 4 天是論文發表，其他則提供短期課程，共有 148 個場次。或許因為在美國首都，又在美國國慶期間，今年論文數應是最近幾年最多者，估計論文總數應有千篇以上。為容納這許多論文，首次有poster session，而不少論文都被分配到poster session，參加人數應有超過千人出席。

會議在暑假期間，又逢美國連續假日，機票很難購得，最後安排在7 月 4 日出發。我與本校郭志文教授一道，經日本飛抵華盛頓。交大林育德教授已先在日本立命館大學訪問，而高雄大學梁明正教授也先在Ohio University 訪問，差不多在同一時間先後抵達會場旅館。

我們的論文是關於電磁相容場衰值的決定方式。目前文獻上已有數種方法可以用來決定場衰，但各有其限制，尤其是學理上需要有無窮大之接地面，這在實際上當然不可能達成。我們透過模擬，提出幾種不同的量測場地幾何配置，可以得到較為一致場衰值的方法。跟一般所使用的方法相比，我們的方法可以減低對場地大小的需求，如果採用，可以節省成本，尤其是在台灣這種寸土寸金的地方。

我們研究成果仍有部份限制，例如在整個寬頻應用時，某些頻點的表現較不理想。另外，

部份設計須利用傾斜的地板，此一部份我們已有傾斜天線取代傾斜地板的方法，有相似

的效果。未來則應到實際的場地再進一步量測，以驗證模擬的結果是否一致。

除了我們的論文外，同行的郭教授及其博士生在SAR 及 FDTD 問題、交大林教授在洩漏波天線、以及梁教授就所設計的天線也都進行報告。這次台灣學界出席會議的有很多人，台大李學智、鄭士康教授，台科大、大同大學、元智也有數位老師參加，中山大學翁金輅教授還有多位以前他指導、現已任教於其他學校的教授們也都出席。整個會議，

台灣出席人員顯得相當活躍。除此之外，各國學者發表的文章，也有不少精采研究成果可供學習、觀摩。

因暑假已開始，會議結束我們幾個人稍有閒情，租車到附近之國家公園遊歷，隨後再安排經日本停留後轉回台灣，結束整個研討會行程。

二、與會心得

此次研討會不只是天線與傳播，因為與URSI 合辦的關係，論文不但在量的方面增加不少，研究的範圍也很更廣，有一些收獲。

可以看出Ultra wideband 是一個熱門的課題，出現在多個 sessions，不但是天線，元件、

系統及傳播也都要能配合ultra wideband，故有很多的論文研究。另隨著無線通訊的發展，電磁波與人體的交互作用更為密切，除了SAR 的問題外，範圍並擴及利用人體來幫忙電磁波的傳播，以及設計更能與人體搭配的天線。另外meta-material 的研究，一直出現一些令人驚異的結果，所以也有非常多的論文探討，不過感覺上，似乎仍有部份基本問題待釐清。數值方法的發展，使得適用的問題更廣，也都有不少的論文。

RFID 由於 Wal-Mart 宣佈要採用，近來也很受國內外產學界的注意，但本次研討會中相關的論文相對分散。感覺起來，技術上可以做的大致已完成，一些瓶頸則仍待突破，而應用的場景仍待辨識出。

三、建議

1. 國內天線及電波傳播界過去數年來參加 IEEE APS 甚為踴躍，表示在天線及傳播方面國內研究也相當活躍，可以在國際學術界更有影響力，值得繼續鼓勵。

2. 隨著國內高等教育蓬勃發展，在國內攻讀博士班的研究生也不少。出國參加研討會是他們可以增廣見聞的一個方式，也應值得繼續加以鼓勵。然而英文能力仍有待加強之處。

四、攜回資料名稱及內容

攜回研討會之會議記錄光碟片一片。

五、其它 無。

附件二、出席國際學術會議發表之論文

A Modified Standard Site Method to Reduce the Effect of a Finite-Size Ground Plane

Kai-Wen Kevin Tien* and Ken-Huang Lin

Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan

This study proposes a new calibration method which can reduce antenna factor variations obtained by using Standard Site Method in a finite-size ground plane.

The investigation has been performed numerically with the method of moments in the horizontal and vertical polarizations. Furthermore, the influences of ground size in calibration measurement are analyzed and a new calibration model is also carried out.

Introduction

ANSI C63.7 [1] defines the geometry of electromagnetic interference (EMI) measurement in open area test sites (OATS). In this standard, the theoretical minimum ground plane size and shape is that of the first Fresnel ellipse. In 3m measurements, CISPR16 [2] uses a 6 m × 9 m ground plane, but ANSI C63.7 indicates that the ellipse is 9.9 m × 9.5 m at 30MHz due to the fact that the 6 m × 9 m ground size is not adequate for vertical polarization. This means that a smaller ground plane could cause measurement errors at a distance of 3 m at lower frequencies. In addition, Standard Site Method (SSM) [3] is often used to calibrate antenna factor (AF) of an antenna, and is conducted primarily in horizontal polarization because measurements in vertical polarization cause larger errors than those in horizontal polarization. Our study therefore investigates the effect of a finite-size ground plane on antenna calibration at a distance of 3 m, and provides a modified calibration method to reduce AF variations obtained over a small size ground plane (3 m × 3 m) to reach levels close to AF variations obtained over a 10 m × 10 m ground plane at lower frequencies. Discussions and simulation results are described in the following sections.

Numerical Model of Antenna Calibration

Fig. 1 shows the geometry of antenna calibration in SSM. We carry out the calibration simulation by using two identical Bilog antennas. AF values therefore can be obtained by

AF = 0.5*(

A

+ 20 log∗

f

_M − 48.92 + E_Dmax)

(1) where

f is the measured frequency in MHz,

_M A is the site attenuation and

is the maximum electric field strength in the receive antenna height-scan range (1–4 m) from a half-wave dipole with 1 pW of radiated power. However,

max

E

the realistic calibration is generally conducted over a finite-size ground plane.

Our simulations therefore are performed over the ground planes with a size of 10 m × 10 m and a size of 3 m × 3 m. AF values for the two cases are calculated by using SuperNEC, a simulation software based on the method of moment (MoM).

Figs. 2 and 3 show two modified calibration methods we proposed: tilt antenna method and tilt ground method. Tilt antenna method is to tilt the transmit antenna to the ground by an angle

θ

. On the other hand, tilt ground method is to tilt the ground plane down by an angle

θ

at the transmit side. Both methods are applied in the calibration over a 3 m × 3 m ground plane and their results will be compared with those obtained by using SSM over a 10 m × 10 m ground plane.

Fig. 1 Calibration geometry in SSM Fig. 2 Tilt antenna method in SSM

Fig. 3 Tilt ground method in SSM Fig. 4 AF variations on a 3m x 3m gr- ound plane in horizontal polarization AF variations arisen from a finite size ground in Standard Site Method

Figs. 4 and 5 show AF variations arisen from a finite-size ground plane (3 m x 3 m) in the horizontal and vertical polarization. AF variations are the differences between AF values obtained on a 3m × 3m ground plane and those obtained on an infinite size ground plane. We can see that AF variations are pronounced at lower frequencies in both figures, and that AF variations in vertical polarization are larger than those in horizontal polarization at frequencies lower than 90 MHz.

The maximum AF variation at frequency 90 MHz is 1.8 dB in vertical polarization and is 1.2 dB in horizontal polarization. We propose tilt antenna method and tilt ground method that can effectively reduce these variations.

Reduction of AF variation by using the tilt methods

The previous AF variations arisen from a finite-size ground plane at 3 m distance of SSM are obviously reduced by our tilt methods at lower frequencies, and the results are shown in Figs. 6–9. In the figures, SSM3 denotes that SSM is conducted at a distance of 3 m.

Fig. 5 AF variations on a 3m x 3m gr- ound plane in vertical polarization

Fig. 6 Comparison of AF variations at 3 m distance between SSM and tilt ground method (horizontal polar.)

Fig. 7 Comparison of AF variations

at 3 m distance between SSM and tilt antenna method (horizontal polar.)

Fig. 8 Comparison of AF variations at 3 m distance between SSM and tilt antenna method (vertical polar.)

Fig. 9 Comparison of AF variations at 3 m distance between SSM and tilt antenna method (vertical polar.)

We show the improvement of AF variations only at the frequencies of 30–90 MHz and 130–280 MHz because the variations at these frequency ranges are larger.

For horizontal polarization, the tilt ground method can reduce AF variations by 1 dB at a frequency of 90 MHz (see Fig.6) and the tilt antenna method can reduce AF variation by 0.5 dB at a frequency of 260MHz (see Fig.7). On the other hand, for vertical polarization, the tilt antenna method can also obviously reduce AF variation to a level lower than 0.1 dB at frequencies of 90 MHz and 260 MHz, which are even lower than the variations obtained on the 10m × 10m ground plane (see Figs. 8 and 9).

Conclusion

This paper proposes two tilt methods which can effectively reduce AF variations arisen from a finite-size ground plane at lower frequencies in SSM. Numerical simulations for this study are implemented by using the method of moment. Our results show that a 3 m × 3 m ground plane can be used for calibration at a distance of 3 m in SSM if the tilt methods are applied.

Acknowledgment

The authors would like to thank Mr. H. F. Chen for his helpful discussions and assistance. This work was partially supported by NSC under the grants NSC93-2213-E-110-008 and NSC92-2213-E-110-001.

References

[1] ANSI C63.7-1992, American National Standard Guide for Construction of Open-Area Test Sites for Performing Radiated Emission Measurements.

[2] CISPR Publication 16 (1987), CISPR Specification for Radio Interference Measuring Apparatus and Measurement Methods, 2nd ed.

[3] A. A. Smith, JR., “Standard-site method for determining antenna factors,”

IEEE Trans. Electromagn. Compat., vol.24, pp.316–322, 1982

在文檔中開放測試場正規化場衰理論值探討及量測不確定度之研究(III)A Theoretical Investigation of Normalized Site Attenuation and a Statistical Study of Measurement Uncertainty in OATS(III) (頁 70-76)